Working with objects

Current learning objective

Assignment to object

• You can assign values to objects using <- or = or even ->
• Just be consistent which one you use!
• The name of the object can be variable so long as it is syntactically valid (no spaces and most special characters, and the name cannot start with a digit)

Vectors

• We can combine scalars to form vectors using c():

Vector types

• There are four primary types of atomic vectors: logical, integer, double and character.

• The integer and double vectors are collectively called numeric vectors.

Vector

• A vector can only consist of the same type
• If you attempt to combine mismatched types together, it will try to coerce all values to the same type.

Casting to other types

• as.numeric() tries to coerce input to numeric value.
• If a logical value is coerced to numeric or integer, then
  • TRUE is 1 and
  • FALSE is 0.

Factor

• A factor in R is a special type of integer vector used typically to encode categorical variables.

Lists

• Lists allow to combine elements of different types.

• You can use str() to see the internal structure of an object in R.

Data frames

• data.frame is a special type of a named list where each element of the vector is the same length.

Subsetting vectors Part 1

• Positive integers select elements at the specified positions:

Subsetting vectors Part 2

• Logical vectors select elements where logical value is TRUE.

• If the logical vector used for subsetting a vector is shorter than it then the logical vector is recycled to match the length of the vector.

Subsetting named vectors

• Character vectors select elements based on the name of the vector (if any):

Subsetting lists

Subsetting named lists

Subsetting data frames

Numerical summaries

• Numerical summaries generally come base or stats package.
• Some common numerical summaries include:
  • Mean: mean()
  • Median: median()
  • Five number summary: fivenum()
  • Minimum: min()
  • Maximum: max()
  • Quantile: quantile()
  • Correlation coefficient: cor()

Missing values

Summary